U.S. patent number 4,448,490 [Application Number 06/233,867] was granted by the patent office on 1984-05-15 for liquid crystal matrix display cells piled with non-overlapping display elements.
This patent grant is currently assigned to Hitachi, Ltd.. Invention is credited to Yoshimichi Shibuya, Masami Takahashi.
United States Patent |
4,448,490 |
Shibuya , et al. |
May 15, 1984 |
Liquid crystal matrix display cells piled with non-overlapping
display elements
Abstract
A liquid crystal display device having a plurality of display
sections each formed of a plurality of common electrodes and
corresponding segment electrodes to display a character is
disclosed. The device comprises a plurality of liquid crystal
display elements piled in the direction perpendicular to the
display surface of the device. Each of the liquid crystal display
elements includes ones selected from the above-mentioned common
electrodes and segment electrodes corresponding to the selected
common electrodes to reduce the number of common electrodes
included in each liquid crystal display element, thereby reducing
the number of common electrode leads provided in each liquid
crystal display element.
Inventors: |
Shibuya; Yoshimichi (Mobara,
JP), Takahashi; Masami (Mobara, JP) |
Assignee: |
Hitachi, Ltd. (Tokyo,
JP)
|
Family
ID: |
12929710 |
Appl.
No.: |
06/233,867 |
Filed: |
February 12, 1981 |
Foreign Application Priority Data
|
|
|
|
|
Apr 23, 1980 [JP] |
|
|
55-52969 |
|
Current U.S.
Class: |
349/82; 345/87;
349/143; 349/34 |
Current CPC
Class: |
G09G
3/18 (20130101); G02F 1/1347 (20130101) |
Current International
Class: |
G02F
1/13 (20060101); G02F 1/1347 (20060101); G09G
3/18 (20060101); G02F 001/33 () |
Field of
Search: |
;350/333,334,332,335
;340/765,784 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Corbin; John K.
Assistant Examiner: Lewis; David
Attorney, Agent or Firm: Antonelli, Terry & Wands
Claims
We claim:
1. A liquid crystal device having a plurality of display sections
arranged in at least one row, each of said display sections being
formed of a plurality of common electrodes divided into a plurality
of groups and a plurality of segment electrodes corresponding to
said common electrodes and divided into a plurality of groups, each
common electrode group including a plurality of common electrodes,
each segment electrode group including a plurality of segment
electrodes, common electrodes included in the corresponding common
electrode groups in said plurality of display sections being
connected in common in a single common electrode lead, said single
common electrode lead including plural lead sections connecting
said common electrodes and also said display sections, segment
electrodes included in each segment electrode group in respective
ones of said display sections being connected to a single segment
electrode lead, said single segment electrode lead including plural
lead sections connecting said segment electrode, said liquid
crystal display device including a plurality of liquid crystal
display elements piled in the direction perpendicular to a display
surface of said liquid crystal display device, and, in each display
section, at least one of adjacent common electrodes and
corresponding segment electrodes being arranged in different ones
of the plurality of piled liquid crystal display elements, each of
said liquid crystal display elements comprising first and second
transparent substrates arranged opposite to each other, a liquid
crystal material disposed between said first and second substrates,
said common electrodes of said groups being formed on an inner
surface of said substrate, said segment electrodes being formed on
an inner surface of said second substrate, a power source for
selectively applying voltages having predetermined waveforms
between said common electrodes of selected groups and said segment
electrodes corresponding to said common electrodes of said selected
groups to drive said liquid crystal display element in a time
divisional fashion, and wherein each of the display sections
includes a plurality of display areas, each of the display areas
being delimited by a common electrode and a corresponding segment
electrode, the display areas of one of said plurality of piled
liquid crystal display elements being arranged in non-overlapping
relationship with the display areas of others of said plurality of
piled liquid crystal display elements when viewed in the direction
perpendicular to the display surface of the liquid crystal
device.
2. A liquid crystal display device according to claim 1, wherein
two of said liquid crystal display elements are provided, said
elements being piled to form a two-layer structure.
3. A liquid crystal display device having a plurality of display
sections arranged in at least one row, each of said display
sections being formed of a plurality of common electrodes divided
into a plurality of groups and a plurality of segment electrodes
corresponding to said common electrodes and divided into a
plurality of groups, common electrodes included in the
corresponding common electrode groups in said plurality of display
sections being connected in common to a single common electrode
lead, said single common electrode lead including plural lead
sections connecting said common electrode and also said display
sections, segment electrodes included in each segment electrode
group in respective ones of said display sections being connected
to a single segment electrode lead, said single segment electrode
lead including plural lead sections connecting said segment
electrodes, wherein said liquid crystal display device includes a
plurality of liquid crystal display elements piled in the direction
perpendicular to a display surface of said liquid crystal display
device, each of said liquid crystal display elements comprising
first and second transparent substrates arranged opposite to each
other, a liquid crystal material disposed between said first and
second substrates, common electrodes belonging to selected groups
of said common electrode groups, said common electrodes of said
selected groups being formed on an inner surface of said first
substrate, segment electrodes corresponding to said common
electrodes of said selected groups, said segment electrodes being
formed on an inner surface of said second substrate, a power source
for selectively applying voltages having predetermined waveforms
between said common electrodes of said selected groups and said
segment electrodes corresponding to said common electrodes of said
selected groups to drive said liquid crystal display element in a
time divisional fashion, wherein two of said liquid crystal display
elements are provided, said elements being piled to form a
two-layer structure, and in each of said display sections, said
common electrodes and segment electrodes are arranged to form a
matrix having a plurality of rows and columns, and said common
electrodes are grouped to every one of said rows, wherein a first
one of said first liquid crystal display elements is provided with
common electrodes arranged in odd-numbered rows and with segment
electrodes corresponding to said common electrodes in said
odd-numbered rows, and a second one of said second liquid crystal
display elements is provided with common electrodes arranged in
even-numbered rows and with segment electrodes corresponding to
said common electrodes in said even-numbered rows.
4. A liquid crystal display device according to claim 1, 2 or 3,
wherein each of said liquid crystal display elements is driven by a
driving method of 1/3 bias with a duty factor of 1/4.
5. A liquid crystal display device according to claim 1, 2 or 3,
wherein each of said liquid crystal display elements is driven by a
driving method of 1/3 bias with a duty factor of 1/3.
6. A liquid crystal display device according to claim 1, wherein
said adjacent common electrodes of a display section are arranged
in different ones of said plurality of piled liquid crystal display
elements.
7. A liquid crystal display device according to claim 1, wherein
two liquid crystal display elements are piled to form a two-layer
structure, and said adjacent common electrodes are alternately
arranged in said two piled liquid crystal display elements.
Description
The present invention relates to a liquid crystal display device,
and more particularly to a dot-matrix type liquid crystal display
device in which the power consumption is small and the field of
viewing the display surface can be improved.
The prior art and the present invention and the advantages of the
latter will be described in detail with reference to the
accompanying drawings, in which:
FIG. 1 is a plan view showing the electrode arrangement in an
example of a conventional dot-matrix type liquid crystal display
device;
FIG. 2 is a sectional view taken along the line II--II of FIG.
1;
FIG. 3 is a view showing a display pattern in a display section of
the liquid crystal display device shown in FIGS. 1 and 2;
FIG. 4 is a circuit diagram showing an example of a power circuit
used in the liquid crystal display device shown in FIGS. 1 and
2;
FIG. 5 shows examples of voltage waveforms applied to electrodes
provided in the liquid crystal display device shown in FIGS. 1 and
2;
FIG. 6 graphically shows a relationship between the peak voltage
and the brightness to explain the operating margin;
FIG. 7 is a graph showing a relationship between the driving method
and the operating margin;
FIG. 8 is a graph showing a relationship between the viewing angle
and the saturation and threshold voltages;
FIGS. 9a and 9b show plan view of the electrode arrangment in
different liquid crystal display elements in an embodiment of a
liquid crystal display device according to the present
invention;
FIG. 10 is a sectional view taken along the line X--X of FIG.
9;
FIG. 11 is a circuit diagram showing an example of a power circuit
used in the liquid crystal display device shown in FIGS. 9 and 10;
and
FIG. 12 is a view showing a display pattern in a display section of
the liquid crystal display device shown in FIGS. 9 and 10.
The liquid crystal display device shown in FIGS. 1 and 2 includes
12 display sections arranged in two rows and six columns. The
above-mentioned display device has upper and lower substrates 1 and
2 which are placed opposite to each other and each of which is
formed of a transparent glass plate. On the facing surfaces of the
upper and lower substrates 1 and 2 are formed segment electrodes 3
and 3' and common electrodes 4 and 4'. The segment and common
electrodes are formed of transparent conductive films and arranged
so that a 5.times.8-dot matrix is formed in each display section.
The upper and lower substrates 1 and 2 are spaced apart from each
other by a predetermined distance by means of a sealing agent 6.
The space enclosed with the upper and lower substrates 1 and 2 and
the sealing agent 6 is filled with a liquid crystal material 5.
Each pair of facing segment and common electrodes form one dislay
dot, and such display dots are arranged to form a 5.times.8-dot
matrix in each display section. Accordingly, 40 display dots
display one character in one display section.
In more detail, one of display sections A.sub.1 to A.sub.6 in the
first row, for example, the display section A.sub.1 includes
display dots A.sub.11 to A.sub.81, A.sub.12 to A.sub.82, . . . ,
and A.sub.15 to A.sub.85, each of which is formed of facing segment
and common electrodes 3 and 4. While, one of display sections
B.sub.1 to B.sub.6 in the second row, for example, the display
section B.sub.1 includes display dots B.sub.11 to B.sub.81,
B.sub.12 to B.sub.82, . . . , and B.sub.15 to B.sub.85, each of
which is formed of facing segment and common electrodes 3' and
4'.
Respective segment electrodes 3 of the display dots A.sub.11 to
A.sub.81, A.sub.12 to A.sub.82, . . . , and A.sub.15 to A.sub.85,
which make up the display section A.sub.1, are connected to one of
segment electrode leads 7.sub.1 to 7.sub.5. In more detail, the
segment electrodes 3 of the display dots A.sub.11 to A.sub.81,
those of the display dots A.sub.12 to A.sub.82, those of the
display dots A.sub.13 to A.sub.83, those of the display dots
A.sub.14 to A.sub.84 and those of the display dots A.sub.15 to
A.sub.85 are connected to the leads 7.sub.1, 7.sub.2, 7.sub.3,
7.sub.4 and 7.sub.5, respectively. Further, the common electrodes 4
of the display dots A.sub.11 to A.sub.15, those of the display dots
A.sub.21 to A.sub.25, those of the display dots A.sub.31 to
A.sub.35, those of the display dots A.sub.41 to A.sub.45, those of
the display dots A.sub.51 to A.sub.55, those of the display dots
A.sub.61 to A.sub.65, those of the display dots A.sub.71 to
A.sub.75 and those of the display dots A.sub.81 to A.sub.85 are
connected to common electrode leads 8.sub.1, 8.sub.2, 8.sub.3,
8.sub.4, 8.sub.5, 8.sub.6, 8.sub.7 and 8.sub.8, respectively. Each
of the display sections A.sub.2 to A.sub.6 included in the first
row has the same structure as the display section A.sub.1. In each
of the display sections A.sub. 1 to A.sub.6 included in the first
row, the common electrodes 4 are divided into eight groups which
are arranged in respective rows, and the corresponding groups of
the display sections A.sub.1 to A.sub.6 are commonly connected to
the corresponding one of the common electrode leads 8.sub.1 to
8.sub.8. On the other hand, in each of the display sections A.sub.1
to A.sub.6, the segment electrodes 3 are divided into five groups
which are arranged in respective columns, and the five segment
electrode leads are provided for the five groups of the segment
electrodes, that is, one of the segment electrode groups is
connected to the corresponding one of the segment electrode leads.
The display sections B.sub.1 to B.sub.6 in the second row have the
same structure as the display sections A.sub.1 to A.sub.6. That is,
common electrode leads 10.sub.1 to 10.sub.8 are provided which are
common to the display sections B.sub.1 to B.sub.6, and segment
electrode lead wires 9.sub.1 to 9.sub.5 are provided for each of
the display sections B.sub.1 to B.sub.6.
The segment electrodes 3 and 3' and the common electrodes 4 and 4'
are applied with voltages having predetermined waveforms through
the segment electrode leads and the common electrode leads, and
thus the orientation of liquid crystal molecules in regions
corresponding to a plurality of display dots is selectively varied
to obtain a desired display arranged in two rows and six columns.
Each of the display sections displays one character. For example,
when the display section A.sub.1 displays the character "B", there
is obtained such a pattern as shown in FIG. 3.
According to the conventional driving system, the above-mentioned
liquid crystal display device can be driven by a driving method of
1/8 bias with a duty factor of 1/8 to 1/4 bias with a duty factor
of 1/8. As is known from the optimum bias method, when the
reciprocal of the duty factor and the reciprocal of the optimum
bias value are expressed by N and B, respectively, a relation
B=.sqroot.N+1 holds. Accordingly, the above device is driven, in
usual, by a driving method of 1/4 bias with 1/8 duty factor. In
this case, a power circuit such as shown in FIG. 4 is employed. In
more detail, a supply voltage V.sub.o is applied to an RC parallel
circuit, which includes resistors R.sub.1, R.sub.2, R.sub.3 and
R.sub.4 and capacitors C.sub.1, C.sub.2, C.sub.3 and C.sub.4, to
obtain bias voltages 1/4 V.sub.o, 2/4 V.sub.o, 3/4 V.sub.o and 4/4
V.sub.o. Namely, the supply voltage V.sub.o is divided by a
resistance type voltage division. The bias voltages thus obtained
are applied through a switching circuit 40 to the common electrode
leads 8.sub.1 to 8.sub.8 and 10.sub.1 to 10.sub.8 and the segment
electrode leads 7.sub.1 to 7.sub.5 and 9.sub.1 to 9.sub.5, to drive
the device. The switching circuit 40 is controlled by the output of
a timing pulse generating circuit 41, and determines the waveform
of voltage applied to each electrode lead. For example, in case
where the common electrode lead 8.sub.1 and the segment electrode
lead 7.sub.1 of the display section A.sub.1 are applied with
voltages (a) and (d) shown in FIG. 5, respectively, a potential
difference (g) shown in FIG. 5 appears between the segment and
common electrodes 3 and 4 which form the display dot A.sub.11, and
therefore the display dot A.sub.11 "turns on" . Further, in case
where the common electrode lead 8.sub.2 and the segment electrode
lead 7.sub.2 of the display section A.sub.1 are applied with
voltages (b) and (e) shown in FIG. 5, respectively, a potential
difference (h) shown in FIG. 5 appears between the segment and
common electrodes 3 and 4 forming the display dot A.sub.22, and
therefore the display dot A.sub.22 "turns on". However, in case
where the common electrode lead 8.sub.3 and the segment electrode
lead 7.sub.4 of the display section A.sub.1 are applied with
voltages (c) and (f) shown in FIG. 5, respectively, a potential
difference (i) shown in FIG. 5 appears between the segment and
common electrodes forming the display dot A.sub.34, and therefore
the display dot A.sub.34 does not turn on. As mentioned above, the
voltages having predetermined waveforms are selectively applied
between the common electrode and the corresponding segment
electrode to drive the liquid crystal display device in a time
divisional fashion. The timing pulse generating circuit 41 is
controlled by the manual operation of a keyboard (not shown) or by
the results of an arithmetic operation for the input obtained by
the manual operation of the keyboard, and generates pulse signals
having predetermined sequences.
In the power circuit employing such a resistance type voltage
divider, a power source has to supply the RC parallel circuit shown
in FIG. 4 with a current which is several or several tens of times
as large as a load current, in order to generate stable bias
voltages without being affected by variations in load, for example,
a change in the number of display dots. Therefore, the power
consumption in the RC parallel circuit becomes large and it may be
said that the whole power consumption of the device is determined
by that of the RC parallel circuit. Further, when the device is
driven by the driving method of 1/4 bias with 1/8 duty factor the
operating margin is very small as compared with a case where the
device is driven by the driving method of 1/3 bias with a duty
factor of 1/3, which is used in an ordinary watch, an electronic
desk calculator, and the like, since the bias value is smaller and
the number of time divisions is larger. As a result, when a viewing
angle .theta. (shown in FIG. 2) formed between the normal to the
display surface of the liquid crystal display device and a
direction in which the display surface is viewed, is large, there
is produced the phenomenon that a display dot applied with the
non-selection voltage waveform (i) shown in FIG. 5 looks as if
turned on, that is, a crosstalk is generated. Further, in case
where the visual angle .theta. is small, that is, the display
surface is viewed in substantially normal direction, a display dot
applied with the selection voltage waveform (g) or (h) shown in
FIG. 5 (or a selected dot) lowers the contrast of display to a
large extent. Now, the above-mentioned matters will be explained
below with reference to FIGS. 6, 7 and 8.
FIG. 6 shows a relationship between the brightness at the display
dot and the peak voltage V.sub.o obtained by the power circuit
shown in FIG. 4 or that shown in FIG. 11 described later. In FIG.
6, the curve A indicates a characteristic in case where the
selection voltage waveform is applied to the display dot, and the
curve C indicates a characteristic in case where the non-selection
voltage waveform is applied to the display dot. The peak voltage
V.sub.o is equal to the voltage of a battery E when the power
circuit shown in FIG. 4 is employed, and equal to the maximum
voltage, which is three times as high as the voltage of a battery
E, obtained when the power circuit shown in FIG. 11 is employed.
The brightness is expressed by 100% when the orientation of liquid
crystal molecules is not subjected to any change. A voltage at a
point on the curve A corresponding to the brightness of 50% and a
voltage at a point on the curve B corresponding to the brightness
of 80% are taken as a saturation voltage V.sub.sat and a threshold
voltage V.sub.th, respectively, and the operating margin M is
defined by the following equation: ##EQU1## The operating margin
may be shown in the Figure by the hatched area. A driving voltage
V.sub.dr is set between the saturation voltage V.sub.sat and the
threshold voltage V.sub.th so that the display dots applied with
the selection voltage waveform (that is, the selected points) have
a brightness of about 20% and other display dots have a brightness
of 100%. In case where the operating margin is large, the
brightness of the selected or non-selected point does not vary even
when the curves A and B are shifted to some extent in the direction
of the abscissa. In case where the operating margin is small,
however, according as the curve A or B is slightly shifted, the
position of an intersecting point of the curve A or B with a
straight line C, which is perpendicular to the abscissa at a point
indicating the driving voltage V.sub.dr, varies and therefore the
brightness of the selected or non-selected point is varied. FIG. 7
is a graph showing a relationship between the operating margin and
the driving method. As shown in FIG. 7, the operating margin
becomes small as the duty factor is smaller, provided that the
optimum bias values are taken for the respective duty factors.
The saturation voltage V.sub.sat and the threshold voltage V.sub.th
vary with the direction in which the display surface is viewed.
FIG. 8 is a graph showing a relationship between the viewing angle
.theta. (which is formed between the viewing direction and the
normal to the display surface) and the saturation and threshold
voltages V.sub.sat and V.sub.th. As shown in FIG. 8, both the
saturation voltage V.sub.sat and the threshold voltage V.sub.th
becomes low as the viewing angle .theta. is larger. Accordingly, in
case where the viewing angle .theta. is large, the threshold
voltage V.sub.th shown in FIG. 6 moves to the left, that is, the
curve B is shifted to the left. In this case, if the operating
margin is small, the brightness of the intersecting point of the
curve B with the line C becomes low. In other words, the
non-selected display dot, which is applied with the non-selection
voltage waveform based on the driving voltage V.sub.dr, looks as if
turned on. That is, a crosstalk is generated. On the other hand, in
a case where the viewing angle .theta. is small, the saturation
voltage V.sub.sat shown in FIG. 6 moves to the right, that is, the
curve A is shifted to the right. If the operating margin is small,
the brightness of the intersecting point of the curve A with the
line C becomes high. Thus, the difference in brightness between a
selected display dot applied with the selection voltage waveform
based on the driving voltage V.sub.dr and non-selected display dots
arranged in the neighborhood of the selected display dot, becomes
small, and therefore the contrast of the display is lowered.
As has been explained in the foregoing, the conventional dot-matrix
type liquid crystal display device has drawbacks that the power
consumption is large, and moreover the display is difficult to be
observed, in other words, the field of viewing the display is
narrow.
The above-mentioned difficulties arise not only in the dot-matrix
type liquid crystal display device, but also in case where a
segment type liquid crystal display device, each display section of
which has eight segment electrodes corresponding to seven sides for
forming the numeral "8" and one dot, is driven by a multiplexing
driving method.
Accordingly, it is an object of the present invention to provide a
multi-layered liquid crystal display device which is low in power
consumption and wide in the field of viewing the display.
In order to attain the above object, according to the present
invention, a liquid crystal display device is divided into a
plurality of liquid crystal display elements, which are piled in
the direction perpendicular to the display surface of the liquid
crystal display device to form a multi-layer structure, common
electrodes and segment electrodes in each display section are
divided into a plurality of groups, which are allotted to the
liquid crystal display elements to reduce the number of common
electrode leads in each liquid crystal display element, and thus
the duty factor and bias value for driving in time divisional
fashion each liquid crystal display element are increased, thereby
the operating margin being made large.
Now, the present invention will be explained below in detail using
an embodiment thereof.
FIG. 9 (FIGS. 9a and 9b) is a plan view showing the electrode
arrangement in an embodiment of a dot-matrix type liquid crystal
display device according to the present invention, and FIG. 10 is a
sectional view of the embodiment shown in FIG. 9. Like numerals in
FIGS. 1, 2, 9 and 10 refer to like elements, and therefore
explanation of these numerals is omitted.
Referring to FIGS. 9 and 10, an upper substrate 11 and a lower
substrate 12 are placed opposite to each other, and each of the
substrates 11 and 12 is formed of a transparent glass plate. On the
facing surfaces of the substrates 11 and 12 are formed segment
electrodes 13 and 13' and common electrodes 14 and 14'. The segment
and common electrodes are formed of transparent conductive films,
and one of the segment electrodes and the corresponding one of the
common electrodes face each other to form a display dot. A liquid
crystal material 15 is disposed between the substrates 11 and 12,
and this structure is sealed at the peripheral portion thereof with
a sealing agent to form a first liquid crystal display element 20.
On the back of the first liquid crystal display element 20, a
second liquid crystal display element 30 is closely disposed in a
two layer structure with the first liquid display element 20 so
that the first and second elements 20 and 30 overlap each other in
the direction perpendicular to the display surface 19 of the liquid
crystal display device. The second element 30 includes similarly to
the first element 20 an upper substrate 21, a lower substrate 22,
segment electrodes 23 and 23', common electrodes 24 and 24', a
liquid crystal material 25 and a sealing agent 26, which are made
of the same material as the upper substrate 11, the lower substrate
12, the segment electrodes 13 and 13', the common electrodes 14 and
14', the liquid crystal material 15 and the sealing agent 16,
respectively. In the first liquid crystal display element 20 are
provided those display dots which correspond to alternate display
dots in a predetermined display dot arrangement such as shown in
FIG. 1. Each of the display dots in the first element 20 is formed
of one of the segment electrodes 13 and 13' and the corresponding
one of the common electrodes 14 and 14' facing the segment
electrode. In more detail, the first liquid crystal display element
20 includes segment electrode leads 7.sub.1 to 7.sub.5 for each of
display sections A.sub.1 to A.sub.6 arranged in the first row, and
includes segment electrode leads 9.sub.1 to 9.sub.5 for each of
display sections B.sub.1 to B.sub.6 arranged in the second row.
However, the first element 20 includes only common electrode leads
8.sub.1, 8.sub.3, 8.sub.5, 8.sub.7, 10.sub.1, 10.sub.3, 10.sub.5
and 10.sub.7. Thus, as shown in FIG. 9a for example, as regards the
display section A.sub.1, there are formed in the first liquid
crystal display element 20 display dots A.sub.11 to A.sub.15,
A.sub.31 to A.sub.35, A.sub.51 to A.sub.55 and A.sub.71 to
A.sub.75, and as regards the display section B.sub.1, there are
formed in the first element 20 display dots B.sub.11 to B.sub.15,
B.sub.31 to B.sub.35, B.sub.51 to B.sub.55 and B.sub.71 to
B.sub.75. Further, in the second liquid crystal display element 30
are provided, as shown in FIG. 9b those display dots which
correspond to other alternate display dots in the predetermined
display dot arrangement and each of which is formed of facing ones
of the segment electrodes 23 and 23' and the common electrodes 24
and 24'. The display dots provided in the second liquid crystal
display element 30 are placed at positions corresponding to gaps
between the display dots provided in the first liquid crystal
display element 20. Accordingly, the second liquid crystal display
element 30 includes segment electrode leads 7.sub.1 to 7.sub.5 for
each of the display sections A.sub.1 to A.sub.6 arranged in the
first row and includes segment electrode leads 9.sub.1 to 9.sub.5
for each of the display sections B.sub.1 to B.sub.6 arranged in the
second row, but includes only common electrode leads 8.sub.2,
8.sub.4, 8.sub.6, 8.sub.8, 10.sub.2, 10.sub.4, 10.sub.6 and
10.sub.8. Thus, as regards the display section A.sub.1, there are
formed in the second liquid crystal display element 30 display dots
A.sub.21 to A.sub.25, A.sub.41 to A.sub.45, A.sub.61 to A.sub.65
and A.sub.81 to A.sub.85, and as regards the display section
B.sub.1, there are formed in the second element 30 display dots
B.sub.21 to B.sub.25, B.sub.41 to B.sub.45, B.sub.61 to B.sub.65
and B.sub.81 to B.sub.85.
According to the above-mentioned electrode arrangement, the common
electrodes are provided in every other row for the display sections
included in each of the first and second liquid crystal display
elements 20 and 30. In other words, each of two display rows (one
of which includes the display sections A.sub.1 to A.sub.6 and the
other includes the display sections B.sub.1 to B.sub.6) includes
four common electrode leads, and therefore each of the elements 20
and 30 can be driven with the duty factor of 1/4. In this case, the
optimum bias value for avoiding a decrease in operating margin is
equal to 1/3 on the basis of the previously-mentioned relation
B=.sqroot.N+1. That is, each element can be driven by the driving
method of 1/4 bias with 1/3 duty factor. Accordingly, the operating
margin is larger as compared with the driving method of 1/4 bias
with 1/8 duty factor explained in conjunction with FIGS. 1 and 2.
Further, in case where the 1/3 bias method is employed, only three
kinds of bias voltages are required. Accordingly, a power circuit
can be used which includes a boosting circuit (or the so-called
tripler) such as shown in FIG. 11. The boosting circuit includes an
oscillator part and a boosting part. The oscillator part is
composed of inverters I.sub.1 and I.sub.2, resistors R.sub.1 and
R.sub.2 and a capacitor C.sub.1, and the boosting part includes
inverters I.sub.3 and I.sub.4, capacitors C.sub.2, C.sub.3 and
C.sub.4 and diodes D.sub.1, D.sub.2 and D.sub.3. When the voltage
of the battery E is equal to V (or 1/3 V.sub.o), voltages V (or 1/3
V.sub.o), 2 V (or 2/3 V.sub.o) and 3 V (or 3/3 V.sub.o) are
obtained at the junction of the capacitor C.sub.2 and the diode
D.sub.2, the junction of the capacitor C.sub.3 and the diode
D.sub.3 and the junction of the capacitor C.sub.4 and the diode
D.sub.3, respectively. The voltage of the battery E may be 1.5 V as
usual. This power circuit is used commonly for driving both the
first and second liquid crystal display elements 20 and 30.
A switching circuit 40' and a timing pulse generating circuit 41'
are similar to the switching circuit 40 and the timing pulse
generating circuit 41 shown in FIG. 4, respectively. The voltage
waveforms (g), (h) and (i) shown in FIG. 5 are formed by the
circuits 40' and 41', and are selectively applied between the
common and segment electrodes constituting pairs through the common
electrode leads and segment electrode leads to drive each of the
first and second liquid crystal display elements in a time
divisional fashion. Because of the capacity of an ordinary battery
for use in watch and the load current, it is very difficult to make
a boosting circuit including four or more capacitors. Accordingly,
the 1/4 bias method which requires four kinds of bias voltages such
as shown in FIG. 4, cannot employ such a boosting circuit.
According to the present invention, the power circuit does not
include the resistance type voltage divider, but includes the
boosting circuit. Therefore, the power consumption is less than
about one-tenth of that in the conventional device. Further, unlike
the conventional device, the common electrodes are provided in each
other row. Accordingly, in each display section in each of the
first and second liquid crystal display elements, the spacing
between adjacent common electrodes in each column of display dots
(each of which is about 500 .mu.m.times.500 .mu.m in size) can be
made equal to about 500 .mu.m, though the above spacing is about
100 .mu.m in the conventional device. Thus, adjacent common
electrodes in each column of display dots are never brought into
contact with each other. Furthermore, in case where that spacing
between adjacent common electrodes in each column of display dots
which is observed when the display surface 19 of the liquid crystal
display device including the first and second elements 20 and 30 is
viewed, is made equal to zero, a display pattern such as shown in
FIG. 12 is obtained which is continuous in each column of display
dots and therefore is easy to be viewed.
Additionally, according to the present invention, the operating
margin can be made large. Therefore, even when the viewing angle
.theta. for viewing the display surface 19 of the liquid crystal
display device is large, the crosstalk will be difficult to occur.
Further, when the display surface is viewed in substantially normal
direction, that is, when the viewing angle .theta. is small, the
contrast of the display pattern can be imporved. Accordingly, the
field of viewing the display pattern can be widened.
In the foregoing description, the explanation has been made of a
liquid crystal display device including 12 display sections
arranged in two rows and six columns. However, it is to be
understood that the present invention is not limited to such a
device but is applicable to a liquid crystal display device
including, for example, only six display sections A.sub.1 to
A.sub.6 arranged in a single row. Further, although two liquid
crystal display elements are piled in the above-mentioned
embodiment, three or more liquid crystal display elements may be
used as required.
Further, in the foregoing embodiment, there has been shown the
display section formed of 5.times.8-dot matrix. However, the
present invention is not limited to such a matrix, but can be
applied with the same effect to a 5.times.7-dot matrix,
5.times.6-dot matrix, 5.times.5-dot matrix, or the like. In case
where the 5.times.7-dot matrix is employed, electrodes in each
display section included in the first liquid crystal display
element are arranged to form a 5.times.4-dot matrix, electrodes in
each display section included in the second liquid crystal display
element are arranged to form a 5.times.3-dot matrix, and each of
the first and second elements is driven by the driving method of
1/3 bias with 1/4 duty factor. Further, in case where the
5.times.6-dot matrix is employed, electrodes in each display
section included in each of the first and second liquid crystal
display elements are arranged to form a 5.times.3-dot matrix, and
the first and second display elements are driven by the driving
method of 1/3 bias with 1/3 duty factor. Furthermore, in case where
the 5.times.5-dot matrix is employed, electrodes in each display
section included in the first liquid crystal display element are
arranged to form a 5.times.3-dot matrix, electrodes in each display
section included in the second liquid crystal display element are
arranged to form a 5.times.2-dot matrix, and the first and second
display elements are driven by the driving method of 1/3 bias with
1/3 duty factor.
It will be understood that the present invention is not limited to
the above-mentioned dot-matrix type liquid crystal display devices,
but is also applicable to the previously-mentioned segment type
liquid crystal display device driven by a multiplexing driving
method.
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